1. Field of the Invention
The present invention relates to a technology for establishing communication links in software defined radios (SDRs).
2. Description of the Related Art
Conventionally, radio devices capable of supporting plural communication modes have been proposed. For example, such a radio device is known that includes a transmitting unit and a receiving unit capable of communicating with plural wireless communication networks applying different communication modes, in respective communication modes, a controlling unit that is connected, via the transmitting unit and the receiving unit, to a communication line of a wireless communication network selected from the wireless communication networks, and a traffic information recognizing unit that recognizes traffic information of the communication line based on a reception signal received by the receiving unit. In the radio device, upon connection to a communication line, the control unit selects a wireless communication network having a communication line with a less activity ratio indicated by the traffic information obtained by the traffic information recognizing unit from among the wireless communication networks (for example, Japanese Patent Application Laid-open Publication No. 2000-209644).
Moreover, in recent years, development of an SDR that supports plural communication modes has been active. For example, such an SDR is known that includes a radio unit that receives a radio signal for conversion to a baseband signal, a baseband signal processing unit for processing the baseband signal that can be restructured, and a restructuring unit that restructures the baseband signal processing unit. In the SDR, the restructuring unit restructures only a part of the baseband signal processing unit performing different arithmetic processes between wireless communication modes (for example, Japanese Patent Application Laid-open Publication No. 2004-153800).
In the radio device supporting plural communication modes, it is necessary to match a communication mode thereof to that of a communication counterpart prior to starting communication with the counterpart. Therefore, in the conventional radio devices, prior to starting proper data transmission or reception, it is necessary to communicate, via a dedicated radio channel, with the counterpart to acquire the communication mode of the counterpart to match the communication mode to that of the counterpart. Thus, a link with the communication counterpart is established. Therefore, besides an originally required radio processing circuit for plural communication modes, another radio processing circuit is required for establishing a communication link. As a result, the radio device has a redundant configuration.